The invention relates to a method for operating a control device for a display that is arranged in a motor vehicle. The invention furthermore relates to the control device for the display.
Today instrument cluster display devices for vehicles, especially motor vehicles, have a plurality of display instruments by means of which various vehicle-specific information may be displayed. These display instruments may include analog indicator devices, for instance round mechanical gauges. In modern motor vehicles, these analog indicator devices are increasingly being replaced by liquid crystal displays with indicator fields that visually signal a plurality of measured variables and/or warning signals. For better orientation of a motor vehicle user, some of the display fields are provided as virtual three-dimensional representations. However, this requires a great deal of computing power, in particular when the display fields are updated frequently because of measured variables that change rapidly.
The underlying object of the invention is to provide a method for operating a control device for a display of a motor vehicle and a control device for a display that make it possible for information, in particular vehicle-relevant information, to be displayed by the display promptly and/or in a time-relevant manner and that contribute to improving a quality of a representation of the information.
In accordance with a first aspect, the invention is distinguished by a method for operating a control device for a display that is arranged in a motor vehicle. The control device is embodied to determine display data for at least one display element. The display is embodied for visually signaling the specific display element as a function of the display data determined by the control device for that specific display element. The method includes the following steps: An estimated updating time period for updating the display data for the display element is determined for the specific display element and the specific updating of the display data for the display element is controlled as a function of the estimated updating time period and a pre-specified image rate.
The image rate denotes a number of individual images that are detected or determined in a certain time segment. A vertical frequency represents a number of individual images per second that are for instance displayed on the display. The image rate of the control device may be different from the vertical frequency of the display. The image rate and the vertical frequency are each preferably to be selected such that a continuous image impression may be imparted to the human eye for moved image content. Selecting the image rate as a whole-number factor of the vertical frequency that is smaller than or equal thereto has the advantage that uniform new images may be displayed. For instance, if the vertical frequency is 60 Hz and the image rate is 30 fps, each determined image is displayed twice. Adequate quality of a representation may be attained when the image rate is equal to or greater than the temporal resolution of the human eye. The pre-specified image rate that the control device should have is preferably matched to the vertical frequency of the display.
Advantageously controlling the updating of the display data of the display element as a function of the estimated updating time period makes it possible to keep a desired image rate of the control device approximately constant and thus to use available computing power of the control device in an optimal manner. In particular, it makes it possible not to fall below a desired image rate, or to fall below it in only a few exceptional cases, for instance when there is a fault. Falling below the pre-specified image rate may lead to a motor vehicle user not perceiving a continuous image impression when he looks at the display, but rather seeing so-called stutters. The display element may need to be updated due to changing vehicle data. These changes in the vehicle data may occur at any time. Determining the estimated updating time period makes it possible to decide whether or not it is still possible to perform an update of the display element during a current updating phase so that there is not a drop below the desired image rate. The updating phase may include a first time segment and a second time segment. During the first time segment of the updating phase, display data determined during a preceding updating phase for the specific display elements may be converted to a data format suitable for displaying on the display and written into a suitably embodied graphics memory. During a second time segment of the updating phase, the specific display elements may be updated.
The display element may extend for instance across a pre-specified display range of the display. The display element may be for instance a speedometer, a fuel gauge indicator, a tachometer and/or a model display of the motor vehicle.
A vertical frequency of the display may be pre-specified as constant or variable. During an update of the specific display element, the specific display data are re-determined and for instance stored in the suitably embodied graphics memory. The display data are for instance retrieved from the graphics memory and displayed by means of the display at a constant vertical frequency at regular time intervals. The display may be embodied for instance to display a pre-specified number of pixels. In this case the display data for the specific pixel of the display element include one or a plurality of pixel values.
The updating of the display data may include a plurality of determination steps. The updating of the display data may for instance include determining a display variable as a function of a detected measured variable and/or operating variable. In addition, the updating of the display data may include determining the specific pixel values for the display element. For instance, when there is a change in the motor vehicle speed, as a function of a currently determined motor vehicle speed an updated angular position of a speedometer needle may be determined and the pixels for the display element that includes the speedometer may be determined such that the display element represents on the display the speedometer with a speedometer needle that has the determined angular position.
The specific updating time period for updating the specific display data may vary. A time period for determining the display variable may vary as a function of the determined measured variable and/or operating variable. Furthermore, a temporal additional period for determining the pixels of the specific display element may be at least approximately constant or may vary. The display element may have representational elements that are to be represented and the number and/or size of which remains the same. In this case the additional period for determining the pixels may remain approximately constant. In a speedometer in which the angular position of the speedometer needle represents the vehicle speed, the number of representational elements stays the same, for instance. In a tachometer in which a number of virtual cubes represent the vehicle speed, in particular the number of representational elements to be represented varies, the time period for determining the pixels therefore varies, as a function of the vehicle speed.
In one advantageous embodiment, a remaining time period that is available for updating the display data of the specific display element as a function of the image rate is determined and the specific updating of the display data for the display element is controlled as a function of the remaining time period. The remaining time period may for instance be determined as a function of the duration of the first time segment and as a function of already determined updating time periods for the specific display elements that were already updated during the second time segment of the updating phase. A decision about whether another display element will be updated during the updating phase may be made as a function of the determined remaining time period and the estimated updating time period for the specific display element.
In another advantageous embodiment, the updating of the display data for the display element is controlled as a function of the detection of an updating requirement for the specific display element. This advantageously makes it possible for the updating of the specific display element to be controlled as needed.
In another advantageous embodiment, the specific display element is embodied for signaling a detected operating variable and/or additional information. The updating requirement is representative of a pre-specified deviation between a first value for the operating variable and a second value for the operating variable, which values are detected sequentially in time at a pre-specified time interval, or of a change in the additional information. The updating of the specific display element may thus be controlled as a function of a change in the information to be signaled.
In another advantageous embodiment, a priority is assigned to each display element. The updating of the display data for the display element is controlled as a function of a value that the priority of the specific display element has, wherein the value of the priority of the specific display element is adapted depending on whether the updating of the display data for the display element is performed during the remaining time period or not. This permits display elements that signal important information to make preferential updates when needed, but ensures that the updating of display elements that are assigned a lower priority is not neglected.
In another advantageous embodiment, the estimated updating time period for the specific display element is determined as a function of at least one updating time period detected during the updating of the display data for the display element. This permits the estimated updating time period to be determined in a simple manner.
In another advantageous embodiment, the estimated updating time period for the specific display element is determined as a function of a maximum updating time period that is determined from a pre-specified quantity of updating time periods detected for the display element.
In another advantageous embodiment, the updating time period is detected during the updating of the display data for the display element, and the quantity includes a pre-specified number of the most recently detected updating time periods. Thus the updating time periods for the specific display elements may advantageously be monitored, for instance to detect faults. Furthermore, the estimated updating time period may be determined in a simple manner as a function of the most recently detected updating time periods.
In another advantageous embodiment, the estimated updating time period is determined as a function of the detected operating variable and/or the additional information that is signaled by the display element. The display element may have representational elements whose number and/or size is a function of the operating variable to be signaled and/or additional information. Depending on the detected operating variable and/or the additional information, a variable portion of the estimated updating time period may for instance be determined and the estimated updating time may be determined in a simple and reliable manner.
In accordance with a second aspect, the invention is distinguished by a control device for a display that is arranged in a vehicle. The control device is embodied to determine display data for at least one display element. The display is embodied for visually signaling the specific display element as a function of the display data determined by the control device for that specific display element. The control device is furthermore embodied for determining an estimated updating time period for the specific display element for updating the display data of the display element. The control device is furthermore embodied for controlling the specific updating of the display data for the display element as a function of the estimated updating time period and a pre-specified image rate. Advantageous embodiments of the first aspect of the invention also apply to the second aspect.
Elements having the same design or function are provided the same reference numbers in all of the figures.